Pulmonary infection will be initiated in mice using Listeria monocytogenes and Mycobacterium tuberculosis as pathogenic agents. The accumulation of activated macrophages and specifically sensitized lymphocytes in the lungs will be monitored. Attempts will be made to digest lung tissue in order to obtain macrophages and lymphocytes as dissociated elements. These will be purified by cell separation procedures and their immunological capabilities will be evaluated by in vivo and in vitro tests of cell mediated immunity.